Epsom salts, a strong laxative used in veterinary medicine, is a hydrate, which means that a certain number of water molecules are included in the solid structure. The formula for Epsom salts can be written as MgSO4 · x H2O, where x indicates the number of moles of H2O per mole of MgSO4. When 3.590 g of this hydrate is heated to 250°C, all the water of hydration is lost, leaving 1.753 g of MgSO4. What is the value of x? use correct sig digs
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The first thing we need to do is find out the molecular weight of MgSO4. When we add it up from the periodic table, we arrive at 120.37 g/mol. To see how many mols are left over at the end, we can do a quick calculation of: 1.753g/ 120.37g/mol =.0145 mols of MgSO4.
Too see how much weight the water contributed, all we do is subtract the amount of MgSO4 from the total.
Weight of H20= 3.590g - 1.753g = 1.837g of water
Next, we need to find out how many mols of water are in 1.837g. We do this by dividing it by its molecular weight: 1.837 g/ 18.02 g/mol = .1019 mols of water
lastly, in order to find the the coefficient that goes in front of H20, we divide by the smallest number:
x= .1019/.0145 = 7.030
Please let me know if you need any clarification. I'm always happy to answer your questions.
If it were me, I would just put 7 because x in this case is a coefficient in the formula, as you said.
All sig digs means is that if you were given 3 decimal places in the question, you can have that in your answer. If it is work for your teacher and he/she is strict about it, I would show my work and write: x = 7.030 , x = 7